Apparatus and method for dispersing and comminuting the solid in a solid-liquid mixture

ABSTRACT

An apparatus and method for dispersing and comminuting the solid in a solid-liquid mixture supported in a container which utilizes attritive elements and rotating impellers enclosed in a substantially vertical cylindrical shell whereby the shell is immersed in the mixture and the mixture is circulated from the container into the shell via inlets and out the shell by means of a rotating centrifugal disc assembly mounted below the inlets to the cylindrical shell.

United States Patent [1 1 Lomasney 1 APPARATUS AND METHOD FOR DISPERSING AND COMMINUTING THE SOLID IN A SOLID-LIQUID MIXTURE [76] Inventor: Henry L. Lomasney, P.O. Box

29077, New Orleans, La. 70189 [22] Filed: May 9, 1974 [21] Appl. No.: 468,576

{52] US. Cl. 241/15; 241/22; 241/4604; 241/461 I [51} Int. Cl. B02c 17/16 [58] Field of Search 241/15, 21, 22, 27, 30. 241/46 R, 46 B, 46.04, 46.06, 46.08, 241/4611, 46.17

[56] References Cited UNITED STATES PATENTS Eppenbach 241/461 1 [451 July 1,1975

2,562,024 7/1951 Dunn et a1. 241/4617 X 2,581,414 1/1952 Hochberg 241/22 2,706,621 4/1955 Laird 241/4617 X Primary Examiner-Granville Y. Custer, Jr. Attorney, Agent, or Firm-Roylance, Abrams, Berdo & Kaul [57] ABSTRACT An apparatus and method for dispersing and comminuting the solid in a solid-liquid mixture supported in a container which utilizes attritive elements and rotating impellers enclosed in a substantially vertical cylindrical shell whereby the shell is immersed in the mixture and the mixture is circulated from the container into the shell via inlets and out the shell by means of a rotating centrifugal disc assembly mounted below the inlets to the cylindrical shell.

21 Claims, 10 Drawing Figures 1 APPARATUS AND METHOD FOR DISPERSING AND COMMINUTING THE SOLID IN A SOLID-LIQUID MIXTURE This invention relates to an apparatus and method for dispersing and comminuting the solid in a solid-liquid mixture, and more particularly relates to an apparatus and method for dispersing and comminuting pigment in a liquid paint vehicle.

in the manufacture of paint and other similar substances it is necessary to homogeneously disperse pigments, or other solid substances, throughout the liquid vehicle and, additionally, reduce the size of the particles forming the solid during such dispersal.

In the prior art, various devices have been utilized to accomplish this dispersal and comminution including ball and pebble mills, buhrstone mills and fine media mills. These last mentioned mills utilize as a grinding media such substances as miniature porcelain balls, coarse sand, or steel shot. In these fine media mills, also commonly referred to as sand mills", typically a quantity of sand is enclosed in a vessel and is agitated by rotating discs as the pigment material and vehicle are passed upward through the vessel. A typical apparatus for carrying out this sand grinding process is described in U.S. Pat. Nos. 2,855,156 and 2,581,4l4. As disclosed therein, the solid and liquid mixture are pumped into the bottom of the vessel, are agitated and comminuted in the middle thereof, and are pumped out the top through a screen which separates the grinding media from the dispersed mixture. Similar disclosures are made in U.S. Pat. Nos. 3,134,549 and 3,243,128.

However, these prior art apparatus have certain dis advantages. First, the solid and liquid mixture has to be premixed in order to provide the needed proportions between the solid and the liquid; consequently, this premixing necessitates expensive equipment, the attendance of an operator and additional time consumption for the overall operation. Secondly, the utilization of the pumping devices necessary to pump the premixed mixture or slurry at a controlled input rate into the agitating vessel necessitates expensive valve systems and piping which are difficult to clean and must be monitored. Thirdly, it has been found that the agitating process produces relatively high temperatures due to friction, which in most cases must be relieved by means of providing a cooling jacket around the agitating vessel and a cooling liquid flowing therethrough. Fourthly, it has been found to be reasonably difficult to change the attritive elements, or grinding media, located in the vessel since the vessel has a variety of inlet and outlet pipes connected to various valve systems. Additionally, the entire overall operation of dispersing and comminuting the mixture has been time consuming since it requires time to set up the apparatus, premix the mixture and finally clean the overall apparatus, especially the screens used therein, once the operation is complete. Lastly, these prior art devices can efficiently function only within a limited range of viscosities since highly viscous mixtures cause the grinding media to float upward into the screen located at the top of the vessel causing clogging and sometimes an overflowing of the media and a comingling of the media with the dispersed mixture, and since highly viscous mixtures tend to clog the various valves and pumping equipment utilized.

Accordingly, it is a primary object of the present invention to provide an apparatus and method which can more efficiently, inexpensively and quickly disperse and comminute the solid in a solid-liquid mixture.

Another object of the present invention is to provide an apparatus and method for dispersing and comminuting the solid in a solid-liquid mixture without the necessity of premixing the mixture in a separate tank, controlling input flow rates, or utilizing separate )umping apparatus and valves or a cooling jacket.

Another object of the present invention is to provide an apparatus and method for dispersing and comminuting the solid in a solid'liquid mixture by utilizing particulate attritive elements whereby a comingling of the dispersed and comminuted mixture and the attritive elements is prevented.

Another object of the present invention is to provide a dispersing and comminuting apparatus and method which accommodates mixtures having a large range of viscosities, has a short overall operation time, has a simple cleaning operation and can have the attritive elements simply and quickly changed.

The foregoing objects are attained by providing :1 cylindrical shell immersed in a mixture located in a container wherein the shell has at least one inlet and an outlet through which the mixture is circulated through the shell and a centrifugal circulation assembly for accomplishing this circulation. This assembly comprises a disc mounted below the bottom opening, or outlet, of the shell and below at least one annular ring a predeter mined distance which is less than the smallest dimension of the attritive elements enclosed in the shell. The inlet is preferably located so that the surface of the mixture in the container is midway between the top and bottom of the inlet, so the mixture readily flows into the shell. Rotation of the disc and the ring imparts centrifu gal forces to the mixture located in contact therewith and expels the mixture from the shell and back into the container. The mixture thus circulating through the cylindrical shell is agitated, and thereby dispersed and comminuted, by means of rapidly rotating impellers lo cated within the shell which rotate through the attritive elements also enclosed within the shell. The shell itself is rotatably mounted to a support so that, through frictional forces created by the attritive elements and the rotating impellers, the shell also rotates and, having vanes on the outside thereof, premixes the mixture located in the container.

Additionally, since the shell itself is immersed in the mixture, a separate cooling jacket and coolant is usually not required since the mixture receives heat transmitted by the shell. Because the mixture is circulated through the cylindrical shell, additional pumps and valves are also not required and, furthermore, by utilizing a centrifugal circulation assembly at the bottom outlet of the cylindrical shell, extra screening is not required for the attritive elements in the shell. Because there are no pumps, and consequently no close fitting pump impellers, occasional loss of attritive elements into the mixture in the container is of little or no consequence. Furthermore, these elements may easily be removed and changed by merely removing the centrifugal circulation assembly from the bottom of the shell itself. The setup and cleaning of the entire apparatus is relatively short since the main assembly can be supported on a hydraulically operated lift and the entire apparatus immersed in a cleaning solution and operated. Because there is no possibility of the attritive elements rising upward, because the mixture flow from the container is downwards through the inlet, a large range of viscosities can be handled by the apparatus, limited only by the spaces defined by the centrifugal circulation assembly.

Other objects, advantages and salient features of the present invention will become apparent from the following detailed description which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.

Referring now to the drawings which form a part of this original disclosure:

FIG. 1 is a vertical sectional view of an apparatus in accordance with the present invention;

FIG. 2 is an enlarged front elevation, in partial vertical section, of the lower part of the apparatus;

FIG. 3 is a sectional view taken along lines 3-3 in FIG. 2;

FIG. 4 is a top plan view of the centrifugal disc;

FIG. 5 is an alternate embodiment of the centrifugal circulation assembly;

FIG. 6 is a second alternate embodiment of the centrifugal circulation assembly;

FIG. 7 is a front elevation of the apparatus having removable mixing vanes;

FIG. 8 is a sectional view taken along lines 88 in FIG. 7;

FIG. 9 is a vertical sectional view of a third alternate embodiment of the centrifugal circulation assembly; and

FIG. 10 is a sectional view taken along lines l0l0 in FIG. 9.

Referring now to the drawings in further detail, in FIG. 1 the overall apparatus of the present invention is designated 10 and is supported on a support 12 which comprises a base 14, a vertical hydraulic cylinder 16, a hydraulic piston 18, a horizontal arm rigidly secured to the top of the piston, and a tapered roller bearing 22 coupled at the end of the arm 20. A suitable power system (not shown) is coupled to the hydraulic cylinder to enable the arm 20 and the apparatus 10 attached thereto to be raised and lowered into and out of the container 24 by vertical movement of the piston 18.

Rigidly supported on top of the arm 20 is a suitably powered electrical motor 26 which may be ofa variable speed type. The motor could also be hydraulic or pneumatic. The shaft 28 included in the apparatus 10 is vertically supported in the bearing 22 for rotation and is thereby fixed against vertical movement relative to the arm. A pulley 30 is rigidly coupled at the shafts top and is connected via belt 32 to a second pulley 34 rigidly coupled to the shaft 35 of electrical motor 26. Thus, actuation of the electrical motor 26 causes a concomitant rotation of the shaft 28, such rotation for the subject invention being preferably in the range of 1,400 to 1,700 rpm. for a cylindrical shell 36 having an 8-10 inch diameter.

The cylindrical shell 36, which is preferably formed of abrasive-resistant steel and which defines a cylindrical chamber 38 therein, is rotatably coupled to the shaft 28 by means ofa tapered roller bearing 40 located in a central aperture in the top wall 42 which is secured to the top of the cylindrical shell. Vertical movement of the shell relative to the shaft is prevented by this conventional tapered roller bearing structure. Preferably, as shown, the shaft 28 extends along the longitudinal vertical axis of the cylindrical shell 36. Spaced downward from the top wall 42 is a support plate 44 which is rigidly secured at diametrically opposed points to the inside wall of the shell and has a roller bearing 46 rotatably coupling the plate 44 to the shaft 28. This support plate 44 and the bearing 46 provide stability to the rotating cylindrical shell 36. Located adjacent the bearing 46 is an opening 48 in the cylindrical shell wall to provide access to that hearing.

As best seen in FIGS. 1, 2 and 3, four vanes designated 50, 52, S4 and 56 are coupled to the outside of the shell 36 and extend along a substantial length of the shell itself. These vanes are separated by 90 and are slightly curved as best seen in FIG. 3. Each vane may have a relief aperture 58 at the lower section thereof to avoid excessive agitation of the mixture located in the container 24. Preferably, the vanes extend from above the four equally angularly spaced inlets 60, 62, 64 and 66 in the shell to a position just above the bottom opening or outlet 68 of the shell, as best seen in FIG. 2. The area of the chamber between the inlets and the outlet 68 is the dispersing and comminuting zone 39 and the plane containing the outlet 68 is perpendicular to the axis of the shaft 28.

A series of impellers are evenly spaced along the shaft 28 in zone 39 from a position below the inlets to a position just above the bottom opening 68. These impellers 70, 72, 74 and 76, as seen in FIGS. 1, 2 and 3, are each formed from a flat, steel disc having a central aperture therein for the reception of the shaft 28 and a collar 82 fixedly coupled to the bottom of the disc and concentric with the central aperture. Each collar has a set screw 84 threaded in a suitable bore therein to fix the vertical position of the disc relative to the shaft and rigidly couple the disc to the shaft. As shown in FIGS. 2 and 3, oblong orifices 86 are formed completely through the thickness of each disc, these orifices being located at 90 intervals along each disc at a radius of approximately one-half the overall radius of the disc, such radius of the disc being slightly smaller than the radius of the cylindrical shell 36. The planes containing the top surfaces of the discs are perpendicular to the vertical, longitudinal axis of the shell and the shaft 28.

Preferably, the top impeller is located approximately one third of the distance from the bottom of the inlets to the bottom opening 68 of the cylindrical shell with the remainging impellers evenly spaced downwardly therefrom. Although four impellers are shown, this is only by way of example with any desired number being usable.

At the bottom of the shaft 28 is the centrifugal circulation assembly 88 which comprises a member or disc 90 shown most fully in FIG. 4. As shown, this disc has a threaded central bore 92 for receiving the associated threads 94 on the end of the shaft 28, as best seen in FIG. 2', however, any suitable coupling can be used. Evenly spaced around the circumference of the disc and slightly inward from the edge are a plurality of threaded bores 96, six being shown by way of example. Rotation of the shaft 28 provides rotation to the disc 90.

Preferably, the top of the disc 90 shown in FIG. 2 is spaced a predetermined distance below the bottom opening 68 of the cylindrical shell 36 and forms a gap 98 between the bottom edge of the cylindrical shell and the top of the disc 90, the planes containing the top of the disc and the bottom opening being parallel and perpendicular to the shaft 28.

As shown in FIGS. 2 and 3, an annular ring 100 is supported above the outer portion of the disc 90 and has its inner periphery spaced from the lower outside edge of the cylindrical shell so as to form an annular gap 102 therebetween. Preferably, the plane containing the bottom opening 68 of the cylindrical shell also contains the bottom surface of the annular ring I00. As seen in FIG. 2 and 3, the annular ring 100 has a plurality of bores 104 located therein in positions corresponding to the bores 96 in the disc 90 for the reception of a suitable number of bolts 106 which pass through the bores in the annular ring and have their threaded ends suitably received in the threaded bores 96 in the disc 90. The top surface of the disc 90 and the bottom surface of the annular ring 100 are separated by means of washers I08 interposed between these surfaces and received by the bolts 106. The annular slot 110 formed between the top surface of disc 90 and the bottom surface of annular ring 100 can be varied by means of varying the thickness or number of the washers 108 and, as described in more detail hereinafter, are adjusted so that the gap 98 and the slot 110 are the same height, this height being such that the attritive elements 112 (shown in FIG. 2) cannot pass from the position inside the cylindrical shell out either the slot 110 or the gap. In other words, the vertical height of the gap and the slot are smaller than the smallest dimension of the attritive elements used to carry out the dispersing are comminuting. Although washers are used, as described above, to provide the spacing between the disc and ring, any other suitable means may be used.

In operation, a container 24 such as that shown in FIG. 1 is first charged with a solid-liquid mixture 114 which can consist of a pigment and a suitable paint vehicle. The attritive elements 112, which can be glass beads, steel shot or other suitable small particulate attritor or grinding media, are charged into the chamber via the inlets and are preferably filled to a height which is a substantial percentage and preferably one-half, the distance between the bottom of the inlets and the bottom opening 68 of the shell. The slot 110 and gap 98 are adjusted dimensionally so that the type of attrtive element to be utilized will not pass therethrough. The apparatus 10 is then lowered or immersed into this mixture by means of manipulating the hydraulic cylinder 16 and the associated piston 18. As shown in FIG. 1, it is desirable that the apparatus 10 be immersed in the mixture a predetermined depth which provides that the surface 116 of the mixture is substantially in the middle of the inlets 60, 62, 64 and 66 of the cylindrical shell 36 after the shell is so immersed. Thus, on immersion the mixture flows into the chamber 38 defined by the shell via the inlets and fills up that chamber to a position substantially as shown by 116 in H6. l. In addition to the flow of the mixture into the chamber through the inlets, a certain amount of the mixture flows into the chamber 38 through the slot 110, the annular gap 102 and the gap 98 formed at the bottom of the cylindrical shell in the circulation assembly 88.

After this immersion is complete, the electrical motor 26 is actuated to rotate the shaft 28 at a suitable speed which, as mentioned above, can be in the range of L400 to L700 r.p.m. The rotation of the shaft causes the impellers to rotate, thereby agitating the attritive elements H2 and the mixture 114 located within the chamber as shown in H0. 2. This agitation causes the pigment, or solid, in the liquid, or paint vehicle, to

become dispersed therein and to be comminuted due to the rubbing or shearing action of the rotating impellers and the agitated attritive elements. Additionally, a rubbing action takes place between the attritive elements 112 and the inner surface 118 of the cylindrical shell 36. The oblong orifices 86 in each impeller allow the mixture to flow therethrough nd also adds to the ag itation of the attritive elements, some of which are di rectly contacted by the inner surface defined by those orifices.

Because the disc 90 is rigidly secured to the rotating shaft 28, this disc and the annular ring secured thereto also rotate at approximately 1,400 to l,700 rpm. and by means of centrifugal force propel any of the mixture located in the annular slot and gap 98 out that gap and slot in a substantially horizontal direction and back into the container 24. By so doing a partial vacuum is formed which causes more of the mixture located in the chamber 38 to move downward in that chamber through the orifices 86 and the spaces defined between the outer peripheries of the impellers and shell inner surface 118 and from that chamber into the slot and gap and then to be propelled outward back into the container 24. Since, as previously described, the size of the gap 98 and the slot 110 are smaller than the smallest dimension of the attritive elements 2, none of the attritive elements exits from the chamber but in fact they all remain there and are continuously agitated by the rotating impellers.

As the mixture exits through the centrifugal circulation assembly 88 via slot 110, the mixture 114 located adjacent the inlets flows under gravitational forces into those inlets and into the chamber 38 and zone 39. Thus, a circulation is established which causes the mixture in the container to enter the chamber and be agitated therein which causes a dispersing and comminuting of the solid or pigment in the liquid or paint vehicle, and then to exit through the centrifugal circulation assembly 88 from the chamber 38 back into the mixture located without the chamber and in the container. Because of this flow, the attritive elements 112 are prevented from exiting the chamber 38 via the inlets eventhough these elements commonly rise to about threequarters the distance between the bottoms of the inlets and the shell bottom opening 68 during rotation of the impellers.

Because the cylindrical shell 36 is rotatably supported relative to the shaft 28, the rotation of the shaft, the rotation of the impellers, and the agitation of the attritive elements located within the chamber and in contact with the surface 118 cause the cylindrical shell itself to rotate in the same direction as the rotation of the shaft. Since the vanes located on the outside surface of the shell 36 are immersed in the mixture 114, the rotation imparted to the shell, and thus the vanes, causes the mixture in the container to be agitated or premixed before it enters the chamber 38 for dispersal and comminution. The relief apertures 58 located in the vanes reduce the impact of these rotating vanes on the mixture in the container so that a very violent agitation is prevented. Additionally, a conventional frictiontype caliper brake 120, as for example shown on pages 348 and 349 of volume 2 of the 1971 Edition of the McGraw-Hill Encyclopedia of Science and Technology, is preferably attached to the top of the cylindrical shell 36 and the arm 20 and is utilized to control the rotational speed of the shell itself to about 20 to 30 r.p.m,

such brake allowing for the use of a wide range of con tainer sizes which can safely and efficiently accommodate the apparatus 10 without a problem of the mixture being agitated right out of the container.

Eventhough the shell has a tendency to be frictionally heated by contact of the attritive elements during rotation of the impellers, since the entire shell 36 is immersed in the mixture 114, and cooled thereby. an ad ditional cooling jacket is not necessarily required. Ad ditionally, any heat transferred from the heated shell will reduce the viscosity of the mixture 114 in the container and provides an enhanced premixing to that mix ture by means of the vanes. Furthermore, highly viscous mixtures can be dispersed and comminuted by the spaced annular rings 126 located above the bottom disc 90 having gaps 127 therebetween formed by a suitable washer and bolt arrangement; however, rather than the inner edges of these rings being placed below the bottom edge of the shell. a plurality of slots 128 are formed in the bottom portion of the cylindrical shell 36, with these slots 128 lying in the same planes as the gaps 127 between adjacent annular rings 126 and the lowest ring and the disc 90. Once again, the operation of this alternative circulation assembly is the same as that described above regarding assembly 88 shown in FIG. 2 but provides the desired flow with the use of smaller gap distance and smaller attritive element size.

An added advantage of the alternative embodiments apparatus 10, limited y to those mixtures which can is that for highly viscous mixtures these embodiments P through the Centrifugal clmuhitloh assembly can provide the necessary flow by providing more of a The Operation of the appamhls is continued for 115 centrifugal force to the mixture lying between the rings long as desired and after Teqhimd dispersal and and the disc because of the overall increase of outlet comminution Of IllC mixture is attained, the motor 70 area and ring and disc area to thereby speed the reis halted and the apparatus 10 is removed from the mixmoval of the mixture from the chamber and speed the ture by means of activiating the hydraulic system. To circulation of the mixture from the container into the readily clean the apparatus for use with other types of chamber. mixtures the entire apparatus 10 is immersed in a con- EXAMPLE tainer of cleaning fluid or solvent and merely operated An example of he use of the apparatus described as f i i above' above was performed with an apparatus 10 having an If It IS deslred to remove the 0f 8 inch diameter cylindrical shell 36 which was 54 live elements 112 Comaihed the Chambarr the (115: inches long. The shell enclosed six 5 inch diameter im- 90 is merely unscrewed from the bottom of the shaft 28 pellers Coupled to the Shaft 28. The Shaft was powered and removed, with the attritive elements 112 dropping 30 by an 18 horsepower m motor and was 2 inches from (Ihamhef Via thfi bottom Opening in diameter. The inlets 60, 62, 64, and 66 were approxiln addition to the centrifugal circulation assembly dematdy 4 inches high and 2 inches wide and the disc 90 scribed above and shown in FIGS. 1 and 2, it is contemwas approximately 14 inches in diameter Zone 39 was plated that two additional alternative embodiments for approximateiy 1 inches kmg. Approximatdy 40 this assembly can be constructed and utilized. pounds f round Steel h 12-14 mesh) as h i- Specifically as Show" in 5, a plurality of Spaced tive elements 112 were introduced through the inlets annular rings 122 are Supported y means of the bolt into the chamber 38. A container 24 having approxiand washer arrangement described above, above the mateiy a 30 i h di d a 30 i h h i h was bottom disc 90 with the distance between the bottom h d i h 50 ll f a lid-li id mixture "4 of the shell 36 and the top Of the diSC 90 fi g P containing a titanium dioxide and lampblack pigment rated by a gap 124 receiving the inner edges of the with a liquid vehicle comprising an acrylic and silicone spaced annular rings 122. As before, the spaces 123 be resin l ti ith a it bl l t bl nd, tween adjacent annular rings. the bottom ring and the The time necessary to grind the pigment contained in disc 90, and the bottom of the shell and the top ring are th mixture t th i i l l f Hegman 6 (fi less than any one individual attritive element minor diness) was as indicated below:

Load On Viscosity Fineness of Elapsed Time Motor Temperature In Krebs Grind (in minutes) Ampercs OfSolution (FJ Units (Hcgman Units) 0 4O 8O 2 15 4O 75 5 30 4O 65 S 45 40 40 5+ 90 40 I45 40 s tau 95 I70 33 6 95 I80 32 6+ mension so that these attrtive elements cannot exit This operation was performed without utilizing a septherefrom. The circulation assembly shown in FIG. 5 arate premix tank, a separate cooling jacket and cooloperates in afashion similar to that described above for 60 am, or separate valves or pumps. The cleanup operacirculation assembly 88; however, since this embodition was fast and efficient, requiring less than half the ment has a larger number of spaces therein through time normally taken in known apparatus. which the mixture exits the chamber, the desired flow Turning now to FIGS. 7 and 8, another modified emof the mixture from the shell can be maintained with bodiment of the apparatus 10 is shown. In this embodithe use of smaller sized spaces and, thus smaller sized 6s ment the fixed vanes 50, 52, 54 and 56 of the apparatus attritive elements.

A second alternative embodiment of the circulation assembly is shown in FIG. 6 and utilizes a plurality of shown in FIGS. l-6 are replaced by removable vanes 150., 152, 154 and i515 which are removably supported in sockets 158 which are rigidly coupled to the outside of the shell 36 at 90 intervals. Each of these vanes is vertically supported on one end of an arm 160 which has a pin 162 connected at the other end fitting into the socket 158. The pin 162 is easily removed from the socket 158 but is preferably coupled to the socket for non-rotational movement about a vertical axis by suitable means such as a key and notch arrangement. The remaining structure is the same as that shown in FIGS. l6.

The purpose of this modified vane arrangement is twofold. First, the length of the arm and the surface area of the vanes may be varied by substituting longer or shorter arms, or longer or smaller vanes allowing the rotational speed of the shell 36 to be varied in relation to the viscosity and composition of the mixture being 5 used. Accordingly, this adjustable feature prevents vio lent agitation of less viscous material and allows various sized containers to be used. Additionally, the vanes can be readily removed altogether, allowing higher rotational speed of the shell during the cleaning operation and consequently a shorter cleaning time.

A further modification of the apparatus is shown in FIGS. 9 and 10 wherein a modified centrifugal circulation asembly 188 is fixedly coupled directly to the bottom of a shorter shell 136 and rotates therewith. This arrangement eliminates the necessity of providing a precision fit between the separately rotating centrifugal circulation assembly 88 and shell 36 shown in FIGS. 1-8.

As shown in FIG. 9, the centrifugal circulation assembly 188 comprises a top annular ring 164, a series of intermediate annular rings 166, a bottom ring 168 and a disc 170, all concentrically mounted around the shaft 28 and below the shell 136. The top annular ring 164 is welded, or otherwise securely fastened, concentrically to the bottom of the shell 136 surrounding the bottom outlet 172 of the shell 136. The remaining intermediate rings and the bottom ring are secured together and to the top ring by receiving in suitable slots 174 (see FIG. 10) four upright vanes 176, 178, 180 and 182 which are welded thereto. Alternately, the rings can be secured together by bolts, as described above with regard to FIGS. 1-6, and the upright vanes suitably supported on the rings or the shell. The spacing between the adjacent rings in FIG. 9 is less than the smallest dimension of the attritive elements to be used so these elements cannot escape from the centrifugal circulation assembly 188.

The disc 170 at the bottom of the assembly 188 is secured to the bottom ring 168 by means of bolts 167 to form the bottom member of the assembly 188. The bolt coupling of the bottom disc 170 allows this disc to be readily removed for the removal of the attritive elements located within the shell 136 and assembly 188.

Sockets 158, described above regarding FIGS. 7 and 8, are attached to the outer surface of the shell 136 for the reception of the removable vanes discussed above and shown in FIGS. 7 and 8. These removable vanes can be used in addition to vanes 176, 178, 180 and 182 or, alternatively, these last mentioned vanes can be eliminated and the removable vanes used solely in their place. If the fixed vanes are not used, the rings can be secured together by the bolt and washer arrangement shown in FIGS. 5 and 6.

The remaining parts of the apparatus of FIGS. 9 and 10 are the same as shown in FIG. 1 and the operation is similar to that described above regarding FIGS. 1-6

except that rotation of the centrifugal circulation as sembly 188 is provided exclusively by the rotation of the attritive elements and the mixture inside the chamber 138 defined by the shell 136 and the centrifugal cir- 5 culation assembly 188.

While advantageous embodiments have been chosen to illustrate the present invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. A method for dispersing and comminuting the solid in a solid-liquid mixture comprising the steps of charging a container with the mixture,

introducing the mixture from the container into a chamber located within the container, said chamber containing a large number of particulate attritive elements;

agitating the solid and the liquid in the chamber and grinding the solid in the chamber by agitating said attritive elements, and expelling the solid and liquid from the chamber back into the container.

2. A method according to claim 1 wherein the introducing step includes immersing the chamber within the container a predetermined depth so that the surface of the mixture in the container is substantially midway between the top and bottom of inlets to the chamber.

3. A method according to claim 1 wherein the agitating step includes rotating impellers within the chamber.

4. A method according to claim 3 wherein the comminuting step includes rotating the impellers through attritive elements located within the chamber.

5. A method according to claim 1, wherein the expelling step includes subjecting the mixture at the bottom of the chamber to centrifugal forces and providing an outlet from the chamber through which the mixture exits under the influence of such centrifugal forces.

6. A method for dispersing and comminuting the solid in a solid-liquid mixture comprising the steps of charging a container with the mixture,

introducing the mixture from the container into a chamber located within the container,

agitating the solid and the liquid in the chamber,

grinding the solid in the chamber,

expelling the solid and liquid from the chamber back into the container, and

mixing the liquid and solid in the container simultaneously with the previous steps.

7. In a process in which the solid in a solid-liquid mixture is dispersed and comminuted by means of agitation 55 with attritive elements, the improvement comprising continuously introducing the mixture into the top of a vertical chamber immersed in a container of the mixture and enclosing a plurality of attritive elements,

continuously imparting an agitation to the attritive elements,

continuously expelling the mixture out the bottom of the vertical chamber, and

continuously recirculating at least a portion of said mixture through said vertical chamber.

8. The improvement according to claim 7 wherein the step of expelling includes subjecting the mixture at the bottom of the vertical chamber to centrifugal forces.

9. The improvement according to claim 7 and further including the step of continuously mixing the mixture in the container.

10. An apparatus for dispersing and comminuting the solid in a solid-liquid mixture supported in a container, comprising:

a support;

shell means defining a chamber which encloses a large number of particulate attritive elements;

said shell means coupled to said support and immersed in the mixture supported in the container to a predetermined level;

circulation means, coupled to said shell means, for

circulating the mixture from the container into the chamber and from the chamber into the container; and

agitation means, coupled to said support, for agitating the mixture within said chamber and for agitating the attributive elements within said chamber to disperse and comminute the solid in the mixture.

ll. An apparatus according to claim 10, wherein said agitation means includes a shaft rotatably coupled to said support and extending within said chamber, and

a plurality of impellers coupled to said shaft.

l2. An apparatus for dispersing and comminuting the solid in a solid-liquid mixture supported in a container, comprising:

a support;

shell means for defining a chamber for enclosing attritive elements;

said shell means coupled to said support and immersed in the mixture supported in the container to a predetermined level; circulation means, coupled to said shell means, for circulating the mixture from the container into the chamber and from the chamber into the container;

agitation means, coupled to said support, for agitating the mixture within said chamber and for agitating the attritive elements within said chamber to disperse and comminute the solid in the mixture; and

mixing means, located within the container, for mix ing the mixture supported in the container.

13. An apparatus according to claim 12, wherein said shell means includes a vertical cylindrical shell rotatably coupled to said support.

14. An apparatus according to claim 13 wherein said mixing means includes at least one vane coupled to the outer surface of said shell and in contact with the mixture in the container.

15. An apparatus for dispersing and comminuting the solid in a solid-liquid mixture supported in a container, comprising:

a support;

shell means for defining a chamber for enclosing attritive elements and having at least one inlet and an outlet. said outlet located below said at least one inlet;

said shell means coupled to said support and immersed in the mixture supported in the container to a preoctermined level;

circulation means, coupled to said shell means, for circulating the mixture from the container into the chamber and from the chamber into the container; and

agitation means, coupled to said support, for agitating the mixture within said chamber and for agitating the attritive elements within said chamber to disperse and comminute the solid in the mixture.

16. An apparatus according to claim l5, wherein said circulation means includes a member mounted below said outlet, and at least one annular ring coupled concentrically above said member, wherein a slot is defined between said member and said at least one annular ring through which the mixture exists.

17. An apparatus according to claim 15, wherein said circulation means includes a member mounted a predetermined distance below said outlet and means for rotating said member,

said predetermined distance being smaller than the smallest dimension of the individual attritive elements enclosed within said chamber.

18. An apparatus according to claim 15, wherein said circulation means includes a member mounted below said outlet, means for rotating said member and a plurality of annular rings coupled to said member and arranged above said member, wherein the inner peripheries of said annular rings are located in the gap defined between said shell means outlet and the top of said member and wherein spaces are defined between adjacent annular rings, between the lowermost annular ring, and said member, and between the outlet and the uppermost annular ring,

each space being smaller than the smallest dimension of the individual attritive elements minor dimension.

19. An apparatus according to claim 15, wherein said circulation means includes a member mounted below said outlet, means for rotating said member, a plurality of annular rings coupled to said member and arranged above said member, and a plurality of slots in said shell means located above the outlet thereof,

wherein the inner peripheries of said annular rings are located adjacent the outer surface of said shell means and wherein a gap is defined between adjacent annular rings and between the lowermost annular ring and said member, adjacent ones of said gaps and slots lying in substantially the same plane, each gap and slot being smaller than the smallest dimension of the individual attritive elements.

20. An apparatus according to claim 15 wherein said shell means is substantially circular in crosssection, and

said circulation means comprises at least one annular ring concentrically mounted about the longitudinal axis of said shell means below said outlet.

21. An apparatus according to claim 20, wherein said circulation means is rigidly coupled to said shell means. i 10! F t 

1. A METHOD FOR DISPERSING AND COMMINUTING THE SOLID IN A SOLID-LIQUID MIXTURE COMPRISING THE STEPS OF CHARGING A CONTAINER WITH THE MIXTURE, INTRODUCING THE MIXTURE FROM THE CONTAINER INTO A CHAMBER LOCATED WITHIN THE CONTAINER, SAID CHAMBER CONTAINING A LARGE NUMBER OF PARTICULATE ATTRITIVE ELEMENT, AGITATING THE SOLID AND THE LIQUID IN THE HAMBER AND GRINDING THE SOLID IN THE CHAMBER BY AGITATING SAID ATTRITIVE ELEMENTS, AND EXPELLING THE SOLID AND LIQUID FROM THE CHAMBER BACK INTO THE CONTAINER.
 2. A method according to claim 1 wherein the introducing step includes immersing the chamber within the container a predetermined depth so that the surface of the mixture in the container is substantially midway between the top and bottom of inlets to the chamber.
 3. A method according to claim 1 wherein the agitating step includes rotating impellers within the chamber.
 4. A method according to claim 3 wherein the comminuting step includes rotating the impellers through attritive elements located within the chamber.
 5. A method according to claim 1, wherein the expelling step includes subjecting the mixture at the bottom of the chamber to centrifugal forces and providing an outlet from the chamber through which the mixture exits under the influence of such centrifugal forces.
 6. A method for dispersing and comminuting the solid in a solid-liquid mixture comprising the steps of charging a container with the mixture, introducing the mixture from the container into a chamber located within the container, agitating the solid and the liquid in the chamber, grinding the solid in the chamber, expelling the solid and liquid from the chamber back into the container, and mixing the liquid and solid in the container simultaneously with the previous steps.
 7. In a process in which the solid in a solid-liquid mixture is dispersed and comminuted by means of agitation with attritive elements, the improvement comprising continuously introducing the mixture into the top of a vertical chamber immersed in a container of the mixture and enclosing a plurality of attritive elements, continuously imparting an agitation to the attritive elements, continuously expelling the mixture out the bottom of the vertical chamber, and continuously recirculating at least a portion of said mixture through said vertical chamber.
 8. The improvement according to claim 7 wherein the step of expelling includes subjecting the mixture at the bottom of the vertical chamber to centrifugal forces.
 9. The improvement according to claim 7 and further including the step of continuously mixing the mixture in the container.
 10. An apparatus for dispersing and comminuting the solid in a solid-liquid mixture supported in a container, comprising: a support; shell means defining a chamber which encloses a large number of particulate attritive elements; said shell means coupled to said support and immersed in the mixture supported in the container to a predetermined level; circulation means, coupled to said shell means, for circulating the mixture from the container into the chamber and from the chamber into the container; and agitation means, coupled to said support, for agitating the mixture within said chamber and for agitating the attributive elements within said chamber to disperse and comminute the solid in the mixture.
 11. An apparatus according to claim 10, wherein said agitation means includes a shaft rotaTably coupled to said support and extending within said chamber, and a plurality of impellers coupled to said shaft.
 12. An apparatus for dispersing and comminuting the solid in a solid-liquid mixture supported in a container, comprising: a support; shell means for defining a chamber for enclosing attritive elements; said shell means coupled to said support and immersed in the mixture supported in the container to a predetermined level; circulation means, coupled to said shell means, for circulating the mixture from the container into the chamber and from the chamber into the container; agitation means, coupled to said support, for agitating the mixture within said chamber and for agitating the attritive elements within said chamber to disperse and comminute the solid in the mixture; and mixing means, located within the container, for mixing the mixture supported in the container.
 13. An apparatus according to claim 12, wherein said shell means includes a vertical cylindrical shell rotatably coupled to said support.
 14. An apparatus according to claim 13 wherein said mixing means includes at least one vane coupled to the outer surface of said shell and in contact with the mixture in the container.
 15. An apparatus for dispersing and comminuting the solid in a solid-liquid mixture supported in a container, comprising: a support; shell means for defining a chamber for enclosing attritive elements and having at least one inlet and an outlet, said outlet located below said at least one inlet; said shell means coupled to said support and immersed in the mixture supported in the container to a predetermined level; circulation means, coupled to said shell means, for circulating the mixture from the container into the chamber and from the chamber into the container; and agitation means, coupled to said support, for agitating the mixture within said chamber and for agitating the attritive elements within said chamber to disperse and comminute the solid in the mixture.
 16. An apparatus according to claim 15, wherein said circulation means includes a member mounted below said outlet, and at least one annular ring coupled concentrically above said member, wherein a slot is defined between said member and said at least one annular ring through which the mixture exists.
 17. An apparatus according to claim 15, wherein said circulation means includes a member mounted a predetermined distance below said outlet and means for rotating said member, said predetermined distance being smaller than the smallest dimension of the individual attritive elements enclosed within said chamber.
 18. An apparatus according to claim 15, wherein said circulation means includes a member mounted below said outlet, means for rotating said member and a plurality of annular rings coupled to said member and arranged above said member, wherein the inner peripheries of said annular rings are located in the gap defined between said shell means outlet and the top of said member and wherein spaces are defined between adjacent annular rings, between the lowermost annular ring, and said member, and between the outlet and the uppermost annular ring, each space being smaller than the smallest dimension of the individual attritive elements minor dimension.
 19. An apparatus according to claim 15, wherein said circulation means includes a member mounted below said outlet, means for rotating said member, a plurality of annular rings coupled to said member and arranged above said member, and a plurality of slots in said shell means located above the outlet thereof, wherein the inner peripheries of said annular rings are located adjacent the outer surface of said shell means and wherein a gap is defined between adjacent annular rings and between the lowermost annular ring and said member, adjacent ones of said gaps and slots lying in substantially the same plane, each gap and slot being smaller thAn the smallest dimension of the individual attritive elements.
 20. An apparatus according to claim 15 wherein said shell means is substantially circular in cross-section, and said circulation means comprises at least one annular ring concentrically mounted about the longitudinal axis of said shell means below said outlet.
 21. An apparatus according to claim 20, wherein said circulation means is rigidly coupled to said shell means. 